Substituted biguanides as flotation reagents



Patented Nov. 21, 1939 PATENT orrics SUBSTITUTED BIGUANIDES AS FLOTATION REAGENTS David Walker Jayne, Jr., ld Greenwich, and

Arvid Emil Anderson, New Canaan,

Conn., as-

signors to American Cyanamid Company, New York, N. Y., a corporation of -Maine No Drawing. Application November 19, 1938. Serial No. 241,394

6 Claims. 7 (Cl. 209-466) This invention relates to the froth flotation of metallic minerals, and particularly to the froth flotation of minerals containing copper.

We have found that substituted biguanides,

their salts and their aldehyde condensation prod- .ucts have a specific flotation promoter action, particularlyon copper minerals,.when used in an alkaline circuit. The cheapest types of biguanides are those-having the following form mula: v

35 in which R and R1 are either hydrogen, an alkyl radical or an aryl radical. These materials are very effective and constitute the preferred embodiment of the invention.

In the past, flotation of copper present in a 20 mixed ore containing, for example, lead and zinc minerals, has been effected by floating ofl the copper and lead in the presence of a depressant for zinc, such as sodium cyanide, and then separating copper from lead. This procedure is often 25 unsatisfactory because it is diflicult to get sufficient depression of the undesired constituents of an ore without affecting the copper recovery. The use of the biguanides of the present invention, however, produces excellent recoveries of high grade copper minerals without any appreciable flotation of the undesired constituents although no depressants are added.

No selective flotation of copper minerals occurs. when the standard potassium or sodium 36 ethyl xanthate reagents are used as promoters,

and it is believed that the surprising result obtained with the compounds of the present invention is due to the formation of water-insoluble copper salts which are readily. floatable. This 40 has not been definitely determined, however, and it should be understood that the invention is in :0 sense limited to any particular theory of ac- The mono-aryl substituted biguanides such as 5 phenyl biguanide, tolyl biguanide, xylyl biguanide, cynnvl biguanide, naphthyl biguanide, and the like, or the aldehyde condensation products thereof such as ethylidene o-tolyl'biguanide, furfurylidene (mixed) xylyl biguanide, and the like, are the preferred modifications of the present invention, but other compounds such as ethyl, isopropyl, butyl, etc., biguanides, diphe'nyl bi guanide, phenyl tolyl biguanide, diethyl biguanide, diisopropyl biguanide, phenyl ethyl biguan- 55 ide, phenyl isopropyl biguanide, and the like, and

their condensation products with acetaldehyde, furfuraldehyde, benzaldehyde, etc., mayalso be used and are included within the scope of the invention. I

We have found a progressive'increase in copper recovery as alkyl loading on the phenyl group is increased up to at. least four carbonatoms in the side chains, i. e., cymyl biguanide, but the higher cost of the cymyl derivatives renders their use uneconomic and the cheaper phenyl and tolyl 1o derivatives are preferred. The simple aldehyde derivatives of the preferred mono-aryl substituted biguanides are more effective than the biguanides from which they are derived, the ethylidene derivatives in turn being more efilcient than the methylene. derivatives, and they are cheap enough to be practicable. The invention is, however, not limited'to these preferred embodiments.

Good copper recoveries are obtained if the reagents of the present invention are used in a circuit having a pH of about 9.5, but the best results are obtained at a pH of about 11-12.

- It is an important advantage of the present invention that it can be applied to a flotation process without necessitating any changes in the fiow sheet of the mill. Thus, for example, it makes no difference whether the reagent is added in the grinding circuit or in the flotation machine and the advantages of the present invention may be enjoyed by merely substituting the biguanides for whatever flotation agent was formerly used. It is alsopossible to use ordinary frothing agents since the products of the present invention do not in any way affect their action.

While we have been referring to the use of the free substituted biguanide bases for the flotation of copper minerals, acid salts of these bases, such as the monohydrochloride, can also be used and are included in the present invention. Whether the substituted biguanide is employed in the form of the free base or acid salt makes no difference since the circuit-is sufliciently alkaline to con-'- vert the' salt to the free base immediately upon addition thereto.

The invention will be described in greater de tail in conjunction with the following specific examples which illustrate the application of the invention to certain typical ores.

Example 1 .Five -20 mesh samples, weighing 600 grams each, of a copper ore containing chalcocite, born- 11.04% sulfur and 73.72% insoluble, were -ground Test: it in a steel rod mill so that substantially all of the "In ore would pass through a 65 mesh sieve, the re- Metallurgical r a H d; Concentrate Telling, assays m um Weight Gold co ert A l u. P610611 05. on Y m Rec. Assay Rec. 02- 0!! P6130611 Grams Element ozJton percent percent percent MSG-mixture of sodium diethyl and di secondary butyl dithiophosphates.- 2.48 2.20 121.5 20.03 ass 80.72 11.81 95.48 0.53 0.14 Ethylidene o-tolyl bi mime 2. 51 a 25 65.1 10. 7a a s4 42. 3e 18. 4s 19. as 1. 45 0. 5s Ethylidene mixed xy yl biguanide 2.1% 2. at 147.8 24. 50 5.97 61.95 9.88 95. 25 1.19 0.16

suiting pulp containing 76.31% of 200 mesh product. The pulp was then transferred to a Fagergren flotation machine; a promoter and frother were added, and the material was floated. The results of comparative flotation tests, wherein the only variable was the type of promoter added, are given in the following Table I.

TABLI I Metallurgical results Heads Concentrate Telling Promot/arused Cu, Assay Assay Dlst. per; Cu, l On, On, cen perperpercent wnt cent cent Sodium ethyl xanthate. 2.68 33.00 86.81 0.33 13.19 Mixed xylyl biguanide hydrochloride 2.68 24.80 82.33 0.52 17. 67 I 2-cymyl biguanide hydroc oride.. 2.64 23.00 92.20 0.23 7.80 Ethylidene o-tolyl bignanide hydrochloride.-. 2.68 28.16 87.32 0. 37 12.68 Ethirlidene (mixed) x yyl biguenide hyorochloride 2.72 25.30 96.04 0.12 3.96

Egamplez Comparative flotation tests. similar to those of Example l'were made on a sulfidelead are containing galena and assaying 8.54% lead, 3.10% iron, 1.86% sulfur and 10.22% insoluble. When 0.02 lb./ton oi the standard potassium ethyl zanthate was used as the promoter, an 80% lead recovery was obtained in a concentrate which assayed 73% lead while 0.068 lb./ton oi ethylidene o-tolyl biguanide hydrochloride as the promoter gave 16% lead recovery in a concentrate which assayed 43.3% lead.

Thus, it can be seen that the reagents oi the present invention do not, in general, promote the flotation of metallic minerals other than copper minerals, or those activated with copper.

Example 3 The results of comparative flotation tests are given in the following Table II, the biguanide reagents being added in the grinding circuit and the fifty-fifty mixture of sodium diethyl and disecondary butyl dithiophosphates in the flotation machine. Other conditions are constant in the three tests. a

The above results show that the ethylidene mixed xylyl biguanide and ethyiidene o-tolyl blguanide give more selective flotation of copper in a gold-copper ore than the dithiophosphate reagent. The fifty-flfty mixture of sodium diethyl and disecondary butyl dithiophosphates, however, is a more powerful promoter for gold than either of the reagents covered by the present invention. This permits a more-efiective separation of copper from gold. Since copper compounds are well known cyanicides, the present invention permits important savings in cyanide where gold-copper ores are treated by a combined flotation and cyanide process. In such cases, the value of the presentinvention does not lie inthe recovery of a copper; on the contrary, in many low grade goldcopper ores, the copper is more an undesired impurity than a real metallic value. The economics of treating many such ores depend on the amount of cyanide which must be used as in such cases, cyanide constitutes one of the major costs. The present invention removes a large portion of the undesired copper impurity without serious gold losses and permits the economic treatment by a combined flotation and cyanidation process of low grade ores which otherwise could not be profitably mined and refined.

When copper-containing precious metal ores which are relatively rich in silver are treated by the process described in Example 3, similar results are obtained, the substituted biguanides showing the same selective action in the case of ores containing silver as they do with ores containing gold. 'The economic importance in the case of silver ores is not usually as great as with low grade gold ores, but the savings are nevertheless material and the present invention can be .eiiectivcly used in treating copper-containing silver ores. or silver and gold ores.

What we claim is:

1. A method of froth'flotation which comprises subjecting an aqueous pulp of a meta1lii.'- 'erous mineral to froth flotation in the presence of a reagent included in the group consisting of substituted biguanides having the following for-, mula:

in which R and R1 are members of the group including hydrogen, alkyl radicals and aryl radicals, their acid salts, and their aldehyde condensation products.

'2. A method of froth flotation which comprises subjecting an aqueous pulp of an ore containing copper to froth flotation in the presence of a reagent included in the group consisting of sub stituted biguanides having the following formula:

B NH NE mt-m-t-m in which R and R1 are members of the group including hydrogen, alkyl radicals and aryl radicais, their acid salts, and their aldehyde condensation products, removing therefrom the concentrate rich in copper and rejecting the tailing poor in copper.

3. A method of differential froth notation which comprises subjecting an aqueouspulp of an ore containing copper and other metallic minerals to froth flotation in the presence of a reagent included in the group consisting of substituted biguanides having the following formula:

the group consisting of substituted biguanidee having the following formula:

3 NE NE x- -omi-mn B. in which R and R1 are members of the group including hydrogen, alkyl radicals and aryl radi cals. their acid. salts, and their aldehyde condensation products, removing therefrom the concentrate rich in copper and rejecting the telling poor in copper and rich in zinc and lead.

5. A method of froth flotation according to claim 3 in which the reagent used is an aldehyde condensation product of a substituted biguanide having the following general formula:

" in which R and R1 are members of the group including hydrogen, alkyl radicals and aryl radicals. i

6. A method of froth flotation according to claim 8 in which the reagent'used is an aldehyde condensation product of a substituted biguanide having the following general formula:

1?. r311 NH N-t m t-m R1 in which R and R1 are members of the group including hydrogen, aliwi radicals and aryl radicals.

DAVID W JAYNE. Je. ARVID EMIL ANDERSON v CERTIEICATE 0F CORRECTION. PatentNo. 2,180,926. November 21, 1939. DAVID-MIXER JAYNE, 5PM, ET AL.

It is hereby certified that error appea rsin the printed specification of the above numbered petent requiring correctionas follows: Page 3, secand that the said Letters Patent should read with this cc-rrection therein that the same may conform-to the record of the case in the Patent Office.

igned and sealed this 16th dayof January, A. D. 1910.

1 f i 4 i enry m: Aredale, {Seal} Acting Commissioner of Pa: .fis.

Y and calm, line 11;, claim 5, for the claim reference nmneral 5" read 1'; 

